The invention relates generally to electronic modules and particularly to electronic transceiver modules of small form factor.
Communication systems are widely employed for a variety of purposes ranging from a basic transmission line in public communication channel to a short-distance network such as a LAN (local area network). These systems include various electronic devices that are interconnected with signal carrying media, such as fiber optic cables or electronic cables. Often, at the interface of a cable and a device is one or more transceivers that receive signals from the cable and forward them to the host device, or receive signals from the host device and forward them to the cable.
A transceiver, unlike a simple connector, serves as an interface converter. For example, fiber optic transceivers convert high-speed electrical signals and convert them to high-speed optical signals. An electronic transceiver that can function as a pass-through, an amplifier, or a reformatter of the electronic signal in such a way as to allow it to transmit over longer distances (serial to parallel conversion) also exist.
Transceivers are typically designed to be electrically and/or optically coupled to a host device and to a network. Typically, transceivers are packaged in the form of a module that has a host device end and a network end. At the host device end, the transceiver module may be mounted on a motherboard of a host device and/or mechanically plugged into a panel that is coupled to the host device. At the network end, the transceiver module is mechanically coupled with a cable connector. There are a number of different connector standards that have been used in the past and have evolved into industry standards. These connector standards include but are not limited to MT-RJ, LC, and SC connectors for optical cables, and RJ-45, RJ-11 and BNC for electrical cables. RJ-45 connectors, which are commonly used with Category 5 cables, are the generally preferred electronic cable/connector systems in most LANs. For pluggable modules, the panel of the host device usually has one or more openings that can accommodate standard sized transceiver modules configured with one of these standard connection interfaces.
Standard modules (e.g., MSA standards) include GBIC modules and, more recently, Small Form Factor Pluggable (SFP) modules, both of which are well known in the industry. SFP modules are becoming increasingly preferred over GBIC modules for their smaller size. As communication systems evolve to require more bandwidth, higher module density is needed at the host device panel, calling for smaller modules. Currently, however, use of SFP modules are limited by the fact that they are not large enough to accommodate many standard cable connectors. Since GBIC modules can accommodate larger cable connectors, e.g., an RJ-45 connector jack, the industry is often forced to use GBIC modules even if SFP modules would be more advantageous. Clearly, an SFP module that can accommodate standard cable connectors is needed. However, because the size of a standard cable connector such as an RJ-45 connector is large relative to the small dimensions of SFP, designing an SFP module that can accommodate an RJ-45 connector jack has been challenging.
FIG. 1 depicts a conventional connector jack 10 that is used to mechanically connect a larger module (e.g., a GBIC module) to a cable connector 11. The connector jack 10 includes a set of electrically conductive leads 14 that are partially enclosed in the jack's plastic housing 16 such that the ends are exposed. A first exposed region 12 of the leads are designed to be coupled to a printed circuit board (not shown) while a second exposed region 14 of the connectors are designed to be coupled with the cable connector 11. The first exposed region 12 may be located on any part of the plastic housing 16 as is convenient for coupling to a printed circuit board. The second exposed region 14 are positioned inside a cavity 18 of the plastic housing 16 such that when the cable connector 11 is inserted into the cavity 18, connection(s) will be established between the printed circuit board and the cable. The cavity 18 is sized and shaped to accommodate a standard cable connector, such as an RJ-45 connector used with a CAT-5 cable. The sidewalls of the plastic housing 16 have to be rigid enough to hold the cable connector 11 in place, and the rigidity requires that the cavity 18 be enclosed by walls of a certain minimum thickness x. Naturally, the size and shape of the plastic housing 16 is dictated largely by the dimensions of the cable connector 11.
FIG. 2 depicts a manner in which the conventional connector jack 10 and the printed circuit board are assembled into a conventional GBIC module 20 by being placed inside a metal shell. The connector jack 10 is coupled to a printed circuit board 22 by any of the well-known and suitable means (e.g., a ribbon connector 24), and this connector-board combination is enclosed by a lower shell 26 and an upper shell 28. The lower shell 26 and the upper shell 28, which are made of a material that shields electromagnetic radiation, are attached firmly to each other with screws 29. The metal shells 26, 28 protect the electrical components of the transceiver 20 and shield electromagnetic radiation. A connector cover 26a of the lower module shell 26 and a connector cover 28a of the upper module shell 28 are designed to surround the connector jack 10, further shielding electromagnetic radiation.
FIG. 3 depicts the GBIC module 20 that is assembled in the manner shown in FIG. 2. The assembled GBIC module 20 is substantially encapsulated with the metal shield 26, 28 except for the cavity 18 at the network end and an opening (not shown) at the host end 29. As described above, the GBIC module 20 uses separate mechanisms for holding the cable connector (i.e., plastic housing 16) and for shielding electromagnetic radiation (i.e., the metal shell 26, 28). As both of these functions are usually needed and the dimensions of the plastic housing 16 alone are larger than the dimensions of the entire connector end of an SFP module as dictated by MSA, today's SFP modules are not compatible with standard RJ-45 cable connectors. However, as stated above, there is an increasing need for an SFP module that can accommodate an RJ-45 cable connector.